1. Field of the Invention
The invention relates to an electrostatic discharge protection device, and more particularly, to an electrostatic discharge protection device with internally shrunk doping region at drain end.
2. Description of the Prior Art
Electrostatic discharge (ESD) is a major factor responsible for the damage of electrical overstress (EOS) of most electronic elements or electronic systems. The damaged electronic elements or electronic systems may be either temporarily disabled or permanently destroyed. This kind of unexpected electrical overstress destruction results in the damage of the electronic elements, adversely influencing the integrated circuits (IC) and making the electronic products fail to function.
The causes of the electrostatic discharge may come from various reasons and are usually inevitable. Static charges may accumulate in human bodies, devices, storages equipments during the manufacture, assembly, testing, storage of the electronic elements or electronic systems, even the electronic elements themselves may accumulate static charges. Static charges discharge when objects contact one another and damage takes its toll.
The object to equip the integrated circuits with the electrostatic discharge protection circuit is to protect the integrated circuits from the damage of the electrostatic discharge. The CMOS technique dominates the current semiconductor circuits. The electrostatic discharge may harm the delicate semiconductor chips in many ways. For example, the discharged charges punch through the thin gate insulator inside the elements or harm MOSFET and CMOS. Accordingly, if the integrated circuits are equipped with the electrostatic discharge protection circuit, they may function normally in the presence of the electrostatic discharge. On the contrary, the integrated circuits without the electrostatic discharge protection circuit may not function well in the presence of the electrostatic discharge. Even further, the chip may be partially disabled or potentially destroyed without obvious signs.
In conventional electrostatic discharge protection device architecture, the doping regions in the source or drain are typically connected to the surrounding field oxide layers directly. Hence, as the device undergoes electrostatic discharge testing, such as when electrical current flows from the drain, passes through the channel under the gate and to the source, the electrical current has the tendency to concentrate at the surface of the channel region and destroy the entire device.
Hence, how to improve the architecture of current electrostatic discharge protection device to provide a device with better stability and ability to safely release electrostatic current has become an important task.